US2255596A

US2255596A - Teletypewriter switching system

Info

Publication number: US2255596A
Application number: US306648A
Authority: US
Inventors: Allen R Bonorden
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1939-11-29
Filing date: 1939-11-29
Publication date: 1941-09-09
Anticipated expiration: 1958-09-09

Description

A. R. BONORDEN 2,255,596

TELETYPEWR-ITER SWITCHING SYSTEM Filed Nov. 29, 1959 7 Sheets-Sheetvl Sept. 9, 1941.

/N VEN TOR A. R. BOA/ ORDEN /l/DM A TTRNE Y Sept. 9, 1941- A. R. BONORDEN TELETYIVDEWRITER SWITCHING 'SYSTEM Filed Nov. 29, 1939 7 Sheets-Sheet 2 l /N VEN TOR By A. R. BONORDE N WRSM A TTORNEV Sept 9, 1941- A. R. BoNoRDEN TELETYPEWRITER SWITCHING SY'S'IEIVI 7 sheets-sheet s Filed NOV. 29, 1939 By ARBON 2 AT TORNEV Sept. 9, 1941.

A. R. BONORDEN TELETYPEWRITER SWITCHING SYSTEM '7 Sheets-Sheet 4 Filed NOV. 29, 1939 Sept. 9, 1941.

A. R. BONORDEN TELETYPEWRITER SWITCHING SYSTEM 7 sheets-sheet 5 Filed Nov. 29, 1939 /NVEN A. R. 50N DEN QMJM A TTORNE Y Sept. 9, 1 941. A. R. BONORDEN TELETYPEWRITER SWITCHING SYSTEM Filed Nov. 29, 1939 s l E INVENTOR ,4.R-BONORDEN mm ww um @mi @wn n ...Hl

Sept. 9, 1941.

. A. R. BONORDEN TELETYPEWRITER SWITCHING SYSTEM Filed Nov. 29, 1939 ALARM CIRCUIT v Br '7 Sheets-Sheet 7 RELAY /N7 TIM/N6 CIRCUIT /N VEA/TOR A TTORNE Y Patented Sept. 9, 1941 TELETYPEWRITER SWITCHING SYSTEM Allen R. Bonorden, Plaineld, N. J., assigner to Beil Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York pplicationy November 29, 1939, Serial No. 306,648

11 Claims.

This invention relates to teletypewriter switching systems and more particularly to those systems wherein teletypewriter loop circuits leased to a private company are adapted for connection with each other as desired by the lessee.

A-n object of the invention is to facilitate switching of any one of several loop circuits incoming at a lessees premises'into connection with one or more of the remaining loop circuits.

In information or news transmission systems employed by private establishments, such as pressv associations and other syndicates of this type, it

is highly desirable that news flashes be broadcasted to various cities throughout the country most expeditiously. Switching centers located. on the premises of these establishments' in the larger cities are connected over leased lines or loops terminating at test boards located in local central, or' exchange, oces of the telephone and telegraph operating companies so that should it be desired to send a news flash from one to another of the larger cities, the connection is established through test boards of one or more operating companies to the switching center atl the distant city. When the information is received at the terminating switching center the connection may be extended on a broadcast basis to one or more other cities located in the area of the terminating switching center. For example, a switching center maybe located in each of the following cities in the United States: New York, New York, representing the eastern States; Atlanta, Georgia, the southern States; Chicago, Illinois, the middle States; Denver, Colorado, the mountain States; and San Francisco, California, the western States. Therefore, a news flash beingY received from Chicago by New York, the switching center at New York, upon being advised of the importance of the message, may connect on a broadcast basis the loop connected through from Clncago, to other loops extending to Boston, Massachusetts; Pittsburgh, Pennsylvania; Washington, 'District of Columbia and other cities located inthe eastern States area.

Hereinafter a private establishment which leases lines, or loops, from an operating company is referred to as the customer and the exchange omce of the operating company is referred to as the central office. The leased lines extend from the test board at the local central office to the switching center of the customer, as loops, and these loops usually operate on a split loop basis, that is, one conductor of each loop operates as a send leg for transmitting from the switching center neutraL or open and close, signals to the local. central cnice, and the other operates'as a receive leg for'receiving at the switching center polar signals transmitted from the local central oice. In this case the conductors of each loop respectively extend through series-connected jacks located in a patching panel board at the switching center, and patched to the jacks of each loop as required by traiiic considerations are teletypewrters with keyboards or automatic tape transmitters for transmitting and receive only teletypewriters or receiving reperforators for receiving news flashes or messages. The teletypewriters are connected to continuously receive and transmit messages. The teletypewriters respectively connected to the send legs usually have an attendant for each machine but those connected to the receive leg are usually arranged in groups and each group is supervised by an attendant.

Although the present invention is based on the use of' the split loop method of operation described in the preceding paragraph, it is within the scope of the invention that send only and receive only metallic loops might be used. In this case the receive only loop might be arranged for the transmission of either polar signals or open and close signals.

According to the present invention, the send leg or receive leg of each loop may be selectively connected separately to a send leg oi any one of the remaining loops or, for broadcast purposes, to the send legs of one or more of the remaining loops simultaneously, the connection being established by means of operable keysets. One key of each set is of the three-posi tion type and the other is of the two-position type. The keysets are arranged in groups, there being as many keysets in each group as there are loops and there are as many groups as the tramo Warrants. Connected to each group of keysets is a common group repeater of the one-way type and connected to the corresponding keysets of such groups is a leg repeater also of the one-way type, that is, a leg repeater is connected to the rst keysetsV of all groups, another is connected to the second keysets of all groups, and so on, there being as'many leg repeaters as there are loops.

A feature of the invention resides in regenerating message signals incoming over the receive leg of a loop before repeating them over the send leg of one or more of the remaining loops to the central oice.

Another feature consists of means for causing to'be simply repeated', thatis, without regeneration, over the send leg of one or more loops to the central oflice, those message signals that originate at the local switching center and are transmitted over the send leg of another loop as a message incoming at the central office.

Still another feature is the provision at a customers switching center, of keysets whereof the three-position key of any one of several sets may be operated either in one direction to connect the receive leg of its associated loop to the input side of a group repeater for regeneration of incoming signals or in the other direction to connect the send leg of such loop tothe input side of a group repeater for repeating without regeneration the incoming signals.

Another feature resides in the keysets whereof the two-position key of any one of the several sets, when operated, may operatively connect the output side of the group repeater to the input side of a leg repeater associated with the loop over which the message is to be repeated and to connect the output side of such .leg repeater to the send leg of the loop over whichv the message is to be repeated. y

Another feature is the provision of teletypewriter monitoring on both the send leg and Y the receive leg of each loop and to permit a monitoring teletypewriter to transmit, over the send leg of each loop.

Another feature resides in the method and means for receiving break signals.

Other features reside in the provision for giving alarm signals when the following attempts to repeat signals are made:

(a) Into one group repeater from more than one loop;

(b) Into, one group repeater from. one loop and to repeat simultaneously, the signals from the same group repeater into the same loop;

(c) Into one group repeater from one loop and to repeat signals from a second group repeater into this same loop;

(d) From more than one group repeater into one loop; and

(e) Into more than one group repeater from one loop.

The system shown herein is assumed to employ nine loops extending from a central oiiice test board to a customers switching center, and of the nine, loops I, 2, 3 and 9 are shown. Also shown are three group repeaters so that a maximum of threesimultaneous broadcasts may be cared for.

In the drawings:

Fig. 1 shows a diagrammatic arrangement of the system wherein four loop circuits of two conductors each extend from the central oice test board through a'single line two-spring jackV (not shown) to the customers switching'center where theV conductors of each loop are connected through individual jacks. The conductors of each loop are further extended through monitoring jacks, respectively, and then through a plurality of series-connected operable keysets to a leg repeater al1 of which are shown` in`each horizontal row Yon the drawings. The number of keysets inA each row depends upon the-v requirements of trafc. The keysets are arranged in groups, the correspondingrkeysets connectedto all the loops forming a verticalle or group. The'keysets of eachgroup are connected in series to a group repeater at one end and'to test 'jacks v group repeaters are likewise connected to the alarm circuit. A test jack is connected to each of the leg repeaters.

Fig. 2 shows the relative arrangement of Figs. 3 to S, inclusive.

Figs. 3, 4, 5 and 6 show four loop circuits extending from a test board (in diagrammatic form.) at-a central oiiice to a customers switching center. Each of the loop circuits are shown connected, in series, through three keysets to a leg repeater circuit, the keysets and leg repeater connected in series in the lowest position, or to No. 9 loop, being shown in detail.

Fig. 7 shows two group repeater circuits respectively connected to the first and second keysets of each of the nine loops.

Fig. 8 shows a group repeater circuit connected to the third keyset of each of the nine loops. cuit and the relay interruptor and timing circuit.

Fig. 9 showsthe attendants monitoring teletypewriter arranged for connection to both legs of any one of the loops.

Fig. 10 shows an attendants series-connected teletypewriter arranged for connection at the patching -panel and for transmitting or receiving messages or news flashes over the send'leg or receive leg of any loop. Fig. 10 is also representative of other transmitting and receiving apparatus such as automatic tape transmitter and receiving reperforators which may be patched as traiiic requires to the proper leg. It is to be understood that instrumentalities connected to any receive leg is arranged for operation on polar signals.

A test board shown diagrammatically and designated COB is located at the central oice of Athe operating company. Loops Nos. I to 9 which correspond to customers line circuits in the ordinary teletypewriter private wire system eX- cept that the loops operate on a split loop basis as hereinbefore described, terminate at their respective spring jacks (not shown) mounted in the test board at one end and at the other end, which is the customers switching center, are respectively connected to pairs of single line twospring jacks mounted at a teletypewriter patching panel. Each of the loops` extend from its jacks in the teletypewriter patching panel through another pair lof single line two-spring jacks and the terminals of a plurality of keysets, arranged in series connection, to terminate in a leg repeater, the jacks and keysets being mounted in a switching panel. Keysets IA, IB, IC, etc. together with leg repeater LRI are associated with loop No. I; keysets 2A, 2B, 2C, etc. together with leg repeater .LR2 are associated with loop No. 2;

keysets

3A, 3B, 3C, etc. together with leg repeater LR3 are associated with loop No. 3; and

keysets

9A, 9B, 9C, etc. together with leg repeater LRS are associated with loop No. 9.,

Connected in common to keysets IA, 2A, 3A and 9A is group repeater GRA; connected in common to keysets IB, 2B, 3B and 9B is group repeater GRB, and connected in common with keys IC, 2C, 3C and 9C is group repeater GRC. An alarm circuit AL is co-nnected in common to each of the group repeaters and the leg repeaters, and connected in common with the leg repeaters only is a relay interrupter and timing circuit IT. The leg repeaters LRI, LRZ, LRS and LRS are of the simple one-way type whereas the group repeaters GRA, GRB and GRC are` of both the simple and the regenerative one-way Also .shown in Fig. 8 are the alarm cirkeys, respectively.

Method of operation When a news ash is received over the receive'leg 502 and recorded .at the teletypewriter 'patched to jack 504 and the news is of such importance that it is`desired to broadcast it to Yother cities over several of the other loops, the attendant in charge of the group of teletypewriters to which the teletypewriter recording the news vis assigned, operates rst the in key of keyset 9A associated with the loop over which the news is received, to its right-hand, or reyceive -leg in position and then one or more of the out keys of the sets associated with the remaining loops, provided they are idle, to their position keys will be referred to as in and ou respective send leg out positions, it being understood that only one in key in any row and group may be operated and that no out key l may be operated in the same row containing `an operated in key in establishing either an individual or a broadcast connection.

'I'he circuit of the receive leg when the in Akey yof set 9A is operated to its right, or receive leg in position, completes the circuit which includes the teletypewriter patched' in at Yjack 504, conductor 500, receive monitor jack 508, and conductor 5|0, rand which extends over the inner.. upper and lower operated right-hand spring members, in parallel, and associated contacts on the in key of set 9A, conductor'5ll, contact and outer left armature ofrelay 10|,

',toground, grounded battery (not shown) for .the 'circuit being furnished at the central ofce.

At the outer upper operated right-hand spring 'member andassociated contact of the in key of set 9A a circuit is closed extending from grounded battery 60|, conductor 002, resistance 5,32, conductorv 5|2, contact and outer upper operatedright-hand spring member of the in Busy relay 603 operates and closes at its armature Yand contact a circuit extending from ground, conductor 606, busy lamp 5| 5 to grounded battery. Lamp 5|5 lights` to indicate that a keyset in loop No. 9 is operated. Polarized relay .SI2 #which is included in a bridge of a Wheat-1 stone bridge arrangement comprising, as one arm, conductor 602,'resistance 532, conductors 5|2, 5|3, 5|4 and 628 and winding of relay 603, and asthe remaining arms, the

respective resistances

625, 626 and-521, does not operate at Vthis time;

At Ythe outer lower operated right-hand spring member ofthe in key of set 9A,'a circuit is closed extending from grounded 'battery 102, conductors 103 and 5|6,'resistance 529, operated outer lower right-hand spring member of the Yin key -of keysetY 9A, conductor 511, inner left armature and back contact of relay 104, through the Winding of relay 105, conductor 129, 'resist- .ance 130 to ground connection 1055.Y Relay 105 f keypfset 9Aconductors 5|3, 514 and 028 'through the winding of busy relay 003, conductor V001|, resistance 025, to ground connection 605..

operates and at its left armature and back contact opens the operating circuit for relay 104. At its innermost right armature and Contact relay 105, upon operating, closes an obvious operating circuit` for busy lamp 101 which lights indicating that group repeater GRA which is associated with the rst keysets IA, 2A and 3A, is busy, and that no other in keys of the rst keysets, that is, those designated A, 2A and 3A, should be operated at this time. Polarized relay 108, however, does not operate at this time inasmuch as it forms a part of a balanced Wheatstone bridge. Polarized relay 108V in this respect is like polarized relay BIZ hereinbefore described. The Wheatstone bridge arrangement comprises, one arm, conductors 103 and 5|0, resistance 529, conductor 5 1, inner left armature and back contact of relay 104, the winding of relay 105 when the in key of set 9A is in its right-hand position, or the winding of relay 104 when the in key is in its left-hand position, and as the remaining arms, the respective resistances 130, 13| and 132. Relay 108 does not operate at this time. f

Relay 105, upon operating, closes another ob- Vious circuit which operates relay 10|. Relay 10|, upon operating, transfers conductor 5|| Whichis the previously traced extension of the receive leg 502, froml ground at its outer left armature to conductor 1|2, through the upper winding of polarized relay 1|3 to ground. Relay 10|, upon operating, also transfers at its right armature, conductor'1l4 from the back contact to the front contact of the armature whereby one side of the operating circuit of regenerative repeater magnet 1|5 including grounded positive rbattery 1|9 is extended over conductors 1|1 and .1| 8 to the armature Vofrpolarized receive relay 1|3. Relay 105, upon operating, as hereinbefore Y described, closes still another obvious circuit for operating motor start relay '|09 which operates. Relay 109, upon operating, connects source 1|0 of alternating current to start motor 1|| whereby .the regenerative repeater element 134 in group repeater GRA is started.

'Ihe basic principle of all telegraph regenerative repeaters is to utilize only aV small part of the middle portion of each received impulse to determine the nature of the outgoing pulses'and to control the timing of these outgoing pulses accurately by local means. In the regenerative repeater employed in the system herein described, but not shown in mechanical detail, the synchronous motor drives two sets of cams, the rst set being used to pick out the mid-portions of each Yincoming pulse and the second set to control the timing of the outgoing pulses. A complete disclosure of this type ofY repeater may jbe found in U. S. Patent 2,105,173 granted to W. J.

Zenneret al. on January ll, 1938.

The transfer of conductor 5|| to'conductor 1|2 :includes receive relay 1|3 in the receive .Y jleg of loop No. 9 whereby relay 113 being polarized, now 'follows the signals of positive current and no current" over a circuit extending from grounded battery 1|9 or no battery, left-hand,V or marking, or'right-hand, or

spacing contact and armature of relay 1|3, conf ductors1|9 and 1|1, front contact and right :the winding of repeater magnet 1|5 to ground.

The regenerative element134' of group repeater GRA will regenerate signals similar in magnitude, shape, duration and polarity as those originally transmitted from the point of origin and when one or more loops are selected for the broadcast these regenerated polar signals will lbe repeated as current and no current signal at the leg repeater of each of the selected loops for transmission over the send legs of the selected loops. The circuit for transmitting the regenerated signals to the leg repeaters is not completed until the attendant operates the out keys of the selected loops over which the out- Ygoing signals are to be transmitted. -It is at this time partly completed over two paths, one from the positive pole of grounded battery and the@ other from the negative pole. The path from 'the positive pole begins at grounded battery 12@ and extends over conductor 12I, contact and in- `ner left armature of relay 10|, conductors 122 and 123, to the upper contact and armature of magnet 1I5; and the path from the negative pole begins at grounded battery 1w, and eX- tends over conductor 121 to the lower contact and armature of magnet 1I5. Both paths converge and extend as one path over conductor 124, inner left armature and back contact of relay 125, conductor 125, to the open contacts of Vthe out keys of each of keysets 9A, 3A, ZA and IA in their normal, or right-hand, positions, the path to keyset 9A extending over conductor 5I8.

Inasmuch as the signals are incoming over the receive leg of loop No. 9 and the in key associated with that loop is operated, the out key associated with one or more of the remaining 'loops and the group repeater GRA, should be operated to transmit the regenerated signals to 'and IA are shown in block form zbut a description of the operation of the out key of set 9A which is shown in detail, will suffice for the corresponding -keys in

sets

3A, 2A and IA. Therefore, for

the purpose of illustration, assume that the out key'of set 9A is operated, the circuit path hereinbefore traced to conductors 126 .and 5I8 is extended over the inner contacts and spring members of the out key of set 9A, now closed since the key is operated to its left-hand position, conductor 569, outer contacts and right-hand spring members of the out key of sets SB and 9C in the positions shown, conductor 691, through the winding of polarized relay 6&3 to ground. Relay 628 will follow the regenerated signals and repeat them over the send leg of loop No. Q which in this case is assumed to be one of the selected loops over which the broadcast is being made. This condition in actual practice Would be undesirable in that the news flash would be retransmitted to a place from which it had been received. However, for the purpose of the description herein this assumption is made.

The circuit to the send leg of loop No. 9 may be traced from ground, armature and marking, or left, contact of relay GD8, conductor 699, make contacts and outer left-hand spring members of the out key of set 9A, conductor 52B, break contacts and outer left-hand spring mem- -bers of the out key of set 9B, conductor 52|, break contacts and outer left-hand spring members of out key of set-SC, conductor 5M), lefthand make-before-break contacts of the in key of set 9C', conductorGII, left-hand makebefore-break contacts of the in key of set 9B,

an incoming message.

conductor l522, left-hand make-before-break contacts of the in`key of set V9A (which contacts would -be closed if loop No. VV9 were actually selected foran outgoin'g'lmessage), conductor 509, monitoring jack'5ll1, conductor 585, patching jack v5133 to send leg5I to which grounded battery is connected at the central oice. The operation of the out key of set 5A to its send leg out, or left-hand position also closes a circuit for operatingbusy relayi which in operating lights busy lamp l555. '(Busy relay-503 was hereinbefore-described as being `operated yto indicate thatloop N 0.-9 contained an operated key due to Now it is assumed to be again operated because of loop No. 9 is herein assumed to be selected for an outgoing message.) Thecircuit for operating busy relay 68.3 is substantially thesameasfhereinbefore described except that it is now `closed at the make contact andinner upper left-hand spring member of the out key of set 9A and includes resistance 53| instead of resistance 52,8. Polarized .relay 6I2 which is-inapathparallel to the operating circuit `for busy lamp 603, does not operate at this time.

Anotherr circuit is closed by the operation of the out key of set 9A, which is traceable from ground, inner lower left-hand spring member and Kmake contact ofthe operated key, conductor 523, through the winding of relay M3, conductor vISM to grounded'battery lIE.v Relay `Ill operates and transfers the receive leg 502- which is normally extendedthrough the patching jack 5,94, monitoring jack `5mi, normally closed make-before-:break'contacts on the righthand side of the vin keyof set 9A (in normal position)conductor 524, normally closed makebefore-break'contactsl on the right-hand sideof the Kin 'key of set 3B, conductor Y525, normally closed make-beore-break contacts of the righthand side of the in`key of, set-9C and conductor 6 I6 to the back .contact and, the outer left armature of relay5I3--froma ground connection SI1 toa path traceable toground through the lefthand Winding ofrthe slow-to-release relay GIB. The circuit'just traced exists only when the in key of set ,9A is in anormal position in which it is assumed to be at the present time and it is further assumed, at this time, that the out key only of set 9A is operatedfor sending a message out over loop No. 9.

Receiving Ibreak signal The purpose `of Athe receive leg of the loop being terminated at the winding of relay SIS in the manner described in the preceding paraygraph is to providey for the `reception of a break signal originated at [the 4station to which the message is being transmitted. When the .out -key of set I,9A was operated to its left-hand position in vorder to engage .the send leg Of 100D No. v9 for sending a message to a distant city, relay BIS operated as hereinbefore described. Relay -5I3, upon operating, closes at its lefthand make-b'efore-brea'k contacts a circuit extending Uthrough the yprimary, or left-hand, winding of` relayvl, to ground. Marking current in the receive leg causes relay 6*!8 to operate. When relay 6I 3 operated, current aiding. the effect ofl the marking current in the ,receive leg liows through K the `Asecondary, or right-hand, winding of relayfl 8. Relay SIS, uponoper'ating, closesat its amature and front contact'. an oper- "ating circuit for relay620 andrelay 620 operates. Relay 620, uponoperatin'g,opens at 4its `innerright armature and contact the operating circuit for start relay 88| andat its outer right-hand armar ture and contact opens the circuit including the primary winding of relay 62|. Relay 8|8 being of the slow-to-release type may or may not follow telegraph signals in the receive leg. Relay 820 being also of the slow-to-release type will remainoperated under normal signaling conditions. However, if a spacing signal exceeding the normal duration is received, relay BIB releases and its continued release causes relay 820 to release. The release of relay 828 applies ground at the middle right armature and contact of relay 8|3 to the inner right armature and back contact of relay 620,

conductors

622 and 823, through the winding of startv relay 80|, to grounded positive battery. Start relay 88| operates to start the interrupter and timing circuit IT. Relay 80|, upon operating, closes at its innermost right armature and contact a circuit traceable from ground over conductor 802 through the winding of slow-to-release relay` 883, conductor 804, resistance 885, to grounded battery 808. Relay 803 operates and at its armature and contact removes direct ground from a path which is parallel with the operating circuit of relay 801. Relay 881 which is of the slow-release type now operates in a circuit traceable from grounded battery 806, resistance 808, conductor 808, through the winding of relay 881, contact normally closed at the lower spring of jack 8|8, conductor 882, contact and innermost right-hand armature of relay 80| to ground. Relay'881, upon operating, removes at its armature and contact a ground connection from a path which Vis parallel to the operating circuit of relay SII. from grounded battery 808, resistance 8I2 through the winding of relay 8| I, conductor 8|3, normally closed contact at the upper spring member of jack 8I8, conductor 802, contact and innermost right-hand armature ofv relay 80| to ground. Relay, 8| upon operating, closes at its contact and right-hand armature a path to ground which shunts the winding of relay 803 and relay 883 releases. Relay 803 upon releas- Relay 8|| operates in a circuit traceable ing, closes at its armature and contacta path forshunting the winding of relay 801 and relay 881 releases. Relay 801, upon releasing, closes at its armature and contact a path for shunting the winding of relay 8|| and relay 8|| releases.

Therefore, as long as start relay 80| is operated the armature and contact Vof relay 8|| closes and opens automatically at a frequency determined by the operating time of each of relays 803, 881 and 8||.

This frequency is at the rate of 120 interruptions per minute, approximately.

K The rst closure of the armature and contact of 4relay 8|| causes to be closed a circuit traceable from ground, outer left armature and contact 'of relay 88|, conductor 8| 4, left-hand armature and contact of relay 8| I, left-hand armature and back contact of relay 8|5, through the winding of relay 8I6, through the left-hand winding of relay 8|5, to grounded positive battery 8|1. Relay 8|8 operates but relay SI5 does not operate at this time because the current through the left-hand, or secondary, winding of relay 8|5 is insufficient to operate it. However, the rst re- 8&8 and the secondary winding of relay 8|5, all

tacts of relay 8| after relays BIE and 8|5 have become operated, closes a path from ground, outer left armature and Contact of relay 80|, conductor 8|4, left-hand armature and contact of relay 8| left-hand armature and front contact of relay SI5, through the secondary winding of relay 8|5 to grounded battery 8I1 thereby shunting the Winding of relay 8I6. releases but relay 8|5 is held operated. f The second opening of the left-hand armature and contact of relay 8|| causes relay 8|5 to release. The left-hand armature and contact of relay 8|| have now closed and opened twice and the left-hand armature and front contact of relay 8|5 have closed and opened once. Therefore, left-hand armature and front contact of relay 8|5 close and open at the rate of approximately 60 interruptions per minute as long as start relay 80| remains operated. Relay 8|5, upon operating, closes at its right armature and contacts a circuit traceable from ground, middle right-hand armature and contact of relay 30|, contact and right-hand armature of relay SI5, conductor 845, outer left armature and back contact of relay 8I8, conductor BIS, right-hand normally closed contact of relay 820, through the winding of relay 820, to grounded positive battery 82|. Relay 820 operates and locks up in a circuit traceable from grounded positive battery 82|, through the winding of relay 820, contact and righthand armature of relay 820,

conductors

822 and 823, back to ground on the contact and middle right-hand armature of relay 80 I. Relay 820, upon operating, applies grounded positive battery 8I1 to the contacts and left-hand armature of relay 820, contact and outer lefthand armature of relay 824, conductor 825, lefthand normally closed contact of relay 828, conductor 821, contact and inner left armature of start relay 80|, conductor 828, through the lefthand winding of relay 82|, contact and outer right armature of relay 620, contact and outermost right-hand armature of relay 8|3 to ground. The operating circuit for relay 820 which extends from grounded positive battery 82| through the resistance 829 and the winding of relay 820 has a parallel path which extends from the same battery source through the resistance 830, back contact and right-hand armature of relay 824 to the same ground used for the operating circuit. The first opening of the contacts of relay 8|5 removes the ground at the middle righthand armature of start relay 80| from the parallel paths and thereby permits relay B24 to operate in a circuit traceable from grounded positive battery 82|, resistance 830, through the winding of relay 824, front contact and right armature of relay 820,

conductors

822 and 823, over the contact and middle right armature of relay 88|, to ground. Relay 824, upon operating, opens at its outer left-hand armature and contact the positive potential supply from grounded battery 8|1 and thereby removes battery from conductor 828 which extends through the lefthandwinding of relay 62| as hereinbefore described. Relay 824, upon operating, closes at its inner left-hand armature and contact a cir- Relay 8|5 l Relay 8|8.

gena-see to grounded positive battery 834. The operating circuit for relay 83| likewise has a parallel path extending from grounded battery `834 through resistance 833, back contact and .right-hand armature of relay 844 to ground at the middle right armature and contact of start relay 88|. The second closure of the right-hand armature and contact of relay 8|5 applies ground to a path which shunts the winding of relay 828 causing it to release. The second opening of the right-hand armature and contact of relay 8|5 causes relay 824 to release. The release of relay 824 removes the shunt around relay :864 which operates. Relay 844 upon operating causes relay 826 to operate and lock to the ground on conz ductor A822. The third closing of the contacts of relay 8|5 causes the relay 828 to operate again, and a third opening of the contacts of relay 8|5 causes 4relay 824 to operate again as described above. This second closure of the contacts of -relay 824 causes relay 83| to release. The fourth closure of relay 8|5 contactsn causes relay 828 to release as previously described. The fourth opening of the contacts of relay 8|5 causes relay 824 to release and the release of relay 824 causes the release of relay 844. The release of relay 844 causes the operation of relay 8|8 which now transfers conductor 845 from relay 828 to relay 83|. Hence, the fifth closure of relay 8I5 contacts causes the relay 83| to operate. opening of the contacts of relay 845 causes relay 84,4 to operate again. This operation of relay 844 causes relay 828 to release. The sixth closure of the contacts of relay 8|5 causes the release of relay 83| which, upon releasing, applies Vground at its left-hand normally closed contacts to a circuit traceable `over contact and inner yleft armature of relay 844, contact and inner left armature of relay 8|8, contact and outermost right-hand armature of relay 88|, conductor 835, contact andleft-hand armature of relay 82|, normally closed contacts of relay 6|9, contacts of inner left armature of relay 6|3, through the winding of relay `(H9 to grounded battery 655. The sixth opening of the contacts of relay8l5 causes the release of relay 844, the release of which causes relay 8|8 to release and also removes ground from conductor 835. The cycle described in the foregoing repeats about every six seconds, applying first a battery pulse on conductor 828 of about one-half second duration and then a ground pulse onconductor 835 of about one-half second duration. The ground pulse follows the battery pulse at about four and one-half seconds interval. The sequence of oper ation as just described is `based ona lcontinuous break signal received on the receive leg of loop No. 8 when it is assumed that loop No. Sis being utilized at the customers switching center for an outgoing message. vIf the break signal ceases before a battery pulse followed by a ground pulse is applied to

conductors

828 and 835, respectively, the appearance of these pulses on these conductors which is essential for the operation of the break signal, is'prevented. Assuming that the break signal is suicient to cause-the appearance of battery and ground pulses on

conductors

828 and 835, these pulses cause the break signal to operate as described in the following description.

The battery pulse on conductor 823 causes the operation of relay 82| in a circuit hereinbefore described. Relay 62|, upon operating, closes at its right-hand armature `and contact v`a locking circuit extending from grounded battery- |5,.con ductor 633, through the right-hand winding and The fth fover the right-hand armature and Contact of relay 82| back contact and right-hand armature of relay @I8 to ground at. the innermost righthand contact of relay 8|3. Relay 252i locks up in an operated condition. The next or following ground pulse on conductor '835 causes the operation of relay @i8 by means of a circuit 'hereinbefore described. Relay 'Ei-i8, upon operating, closes a locking circuit for itself which is traceable frcrn Vground atthe inner left armature and front contact of relay 618, front'contact and 'in- `ner-left armature of relay @i3 through the winding'of relay 6|8 to grounded battery '16|5. Relay .6|8 locks itself in an operated condition. Relay m8, upon operating, closes a circuit traceable Ifrom grounded battery 865, outer right armature 'and contact of relay EHS, conductor G24, through the answering lamp 526 to ground. -Larnp 526 lights to indicate to the attendant at lthe switching cen-ter that the :party at Vthe opposite end-of loop No. 9 wishes to interrupt the message. Relayi), upon operating, completes another circuit which is traceable from ground at `the contact and inner right-hand armature of relaylg, conductor 625, through the normally closed contacts of night alarm -key 843, signal bell 835 to grounded battery 83'?. 'The bell operateseproviding an audible alarm operating in conjunction with answering lamp 528 to indicate to -the attendant at the `switching center that a party'norrnally receiving a broadcastedniess'age `desires to send a-rnessage back tothe switching center. Re-

zlay'lg, upon operating, opens at its outer left armature and contact the 4circuit extending 'through the secondary, or right-hand, winding of relay6i8 :thereby permitting =relay @I8 toopcrate-under the influence of the current flowing inithe primary, orleft-hand, windingat the-end of the break signal. Relay 6ta, upon operating, opens at its back contact and armature the locking circuit for relay 82| and at its front contact and armature closes an obvious circuit for .operatingvrelay 628. 'Relay A82| releases. Relay 1.628 operates to'thereby open-'at its inner rightarmature and Acontact the operating circuit Sfo'r start relay 88 i, and at its outer right-.hand armature and contact the circuit including 'battery pulse conductor 828. The relay interrupter and .timing circuit, shown `in Fig. 8, is now ldisassociated from the leg repeater-circuit LR8, associated withiloop No. 8 over which the first `break signal wasreceived. Itstill might be in operation, however, in connection withfaibreak signal received on anotherl of the remaining'loop circuits. Normally, a break signal of about iive 'seconds Iin duration should operate the audible signal. However, ifwtwo -break signals are-received'nearly simultaneously, a break signal of -about ten seconds in duration may be required on the second circuit to operate the lamp and audible signal. The break signals and breakv circuits are restored by operating to its normal, or the right-hand, position the two-.position key-of set "9A which is'assumed to be associatedwith-loop No. 8 on which the break occurs. The attendant atthe switching panel answers the lighted lampwsignal 526 by plugging the ymonitoring teletypewrit'er cord shown in Fig. 9 into monitoring jacks 588 and 581, operating the cord key/to the rightfor send and receive leg, position. He then restores to normal the operated out y-key,thus restoring loop'No. '9 to its former condition. All operated relays irl/the leg repeater LRS restore tol normal, relay 6|9, 'on restoring,.causing lamp -528to\be Vextinguished andthe bell`838 tobe silenced. Two-way lteletypewriter communica- Ytion is now established between the monitoring teletypewriter andthe distant station where the break signal originated.

Transmitiing from a. teletypewriter connected to a jaclc at the patching panel, over a send Zeg of one Zoop to a "send Zeg of one or more of Vthe remaining loops Assume that it is desired to originate a news ilash or message at the customers switching center for transmission over one or more of the remaining loops and that the teletypewriter connected to loop No. 9 is selected. The teletypewriter connected at send leg 50! to jack 593 which is mounted in Ithe patching panel is employed for this purpose. The attendant assigned to this teletypevvriter throws the in, or three-position, key of set 9A at the switching panel to its send in, or left-hand, position and then throws an out, or two-position, key of the keyset for each of the remaining loops over which the news flash or message is to be transmitted, to its respective send out, or left-hand, position. Inasmuch as lthe switching circuit for loop No. 9 is the only one that is shown in detail, it `will be assumed hereinafter for the purpose of the description of the invention that loop No. 9 is also selected as one of the remaining loops over which thernews flash is to be transmitted.

The operation of the in key of set 9A to its send in, or left-hand, position transfers the Y send legi 50 I ,--which normally extends through the teletypewriter at jack 503 in the patching panel, over conductor 505, through the monitoring jack 501, over conductor 509, normally closed contacts on the left side of the in keys of

sets

9A, 9B and 9C, in series, back over the normally closed contacts on the left side of the out keys offsets 9C, 9B and 9A, in series, conductor 521 to ground connection EIL-to conductor 528, normally closed contacts of relay 125 to ground connection 128.

Grounded battery I is connected over conductor 502, resistance 532, contacts and outer upper spring member on the left side of the in key of set 9A, conductor 5|4, through the Winding of busy relay 603, to ground 605. Busy relay 603 operates but relay SI2, which is in the bridge of the Wheatstone bridge arrangement, does not operate at this time. Relay 603, 'upon operating, causes busy lamp I5 to light indieating to the attendant at the switching center that a keyset in loop No. 9 is operated. The in key of set 9A upon being operated to its send leg in, or left-hand, position closes a circuit extending from grounded battery 102, conductors 103 and 516, resistance 529, contact and inner lower left-hand spring member of the in key of set 9A, conductor 530, left-hand armature and back conta-ct of relay 105, through the Windving of relay 104, conductor 129, resistance 130, 1 to ground connection 106. but polarized relay 108, which is in the bridge of a Wheatstone bridge arrangement included Relay 104 operates in the circuit just traced, does not operate. Re-

l lay 104, upon operating, connects at its outer 3 left armature and contact ground to the lower,

or biasing, winding of polarized relay 1I3, through the winding of relay 125 to grounded battery. The circuit just traced, applies biasing current to relay 1I3 and operates relay 125. Re-

. lay 104, upon operating, closes at` its right arma- 1 ture and contact a circuit for operating busy l lamp 101 indicating that a group repeater GRA is busy. Also, relay 104, upon operating, Opens input and output sides of one group.

at its inner left-hand armature and back contact the operating circuit for relay so as t0 prevent any possibility of the regenerative element of group repeater GRA operating at this time. Relay 125, upon operating, transfers conductor 528 from ground connection 128 to the grounded operating, or upper, Winding of polarized relay 1I3 and at its right-hand armature and contacts connects grounded Vpositive battery to the spacing contacts of relay 1I3, grounded negative battery 1I9 being connected to the marking contacts of relay 1I3. Relay 1l3 now follows the signals transmitted by the teletypewriter connected to jack 503 which is connected in the send leg of loop No. 9.

Assume for the purpose of illustration that loop No. 9 is idle and that it is one over which the signals are to be transmitted to a distant station. The out key of set SA is then operated to its send leg out, or left-hand, position. Relay 125, upon operating as described in the previous paragraph, closes at its inner left make-before-break contacts a circuit extending from the armature of relay 1'I3, conductors H8, 126 and 5I8, inner make contacts.

and right-hand spring members of the out key of set 9A and over conductor 5I9 as hereinbefore traced to operate polarized relay 608 of the leg repeater LRS associated with loop No. 9. Polarized relay 608 follows the signals repeated by relay 1I3 and repeats them out over the send leg of loop No. 9 as hereinbefore described for outgoing messages. One or more of the remaining loops may also be employed for repeating the outgoing message by operating the ou key of the corresponding keyset associated with each of the other remaining loops, the leg repeater associated with each of the other remaining loops being connected in parallel with leg repeater LR9 to repeat the signals from relay 1I3 over the send legs of their respectively associated loops.

Alarm for operating errors An audible alarm in the form of buzzer 838 is caused to operate whenever an operating error is made. An operating error may consist of:

(a) Associating more than one loop with the input side of repeater;

(b) Associating the same loop with both the (This function was assumed in the foregoing'description for the purpose of illustration only);

(c) Associating the same loop with the input side of one group repeater and the output side of a second group repeater;

(d) Associating the same loop with the output side of more than one group repeater;

(e) Associating the same loop with the input side of more than one group repeater.

The foregoing errors would occur when more than onekey is operated in any horizontal or Vertical row except that any number of out keys in one vertical' may be operated. The buzzer 838 is operated by the operation of either of the polarized relays SI2 or 108.

As hereinbefore described, the windings of polarized relays SI2 and 108 each comprise the bridge element of a Wheatstone bridge resistance network. It is a well-known characteristic of such a network that values of resistances may be selected for any three so that the current in the bridge element may be reversed by varying the Value of the fourth resistance ann.

Resistances

625, 62B and 621 comprise three arms and polarized relay ||2v the bridge of such a' network. The fourth arm is normally open, i. e.,. of innite resistance. When an in or ou key is operated, a resistance, such as 538 or 53| in series with relay 683, becomes the fourth arm as previously described. The resistance value of relay- 603 is small compared to that of resistances 532 or 53|. In both cases the current in. polar relay SI2 is in such a direction as to hold the relay non-operated. When a second key inA the same horizontal row is operated, a second resistance, such as 532 or 53|, is lconnected in parallel so that the resistance value of the fourth arm is almost halved, resulting in a reversal ofl current in the polar relay SI2 which operates. Resistances 130, '13| and '|32 comprise three arms, and polarized relay '|08 is the bridge of a sirnilar' network which is associated with group repeater GRA. 'Ihe fourth arm in this network, as hereinbefore described, consists of a resistance such as 529 in series with either relay '|04 or relay T85, the resistance of the relay winding being low compared with that of resistance 529. When `either relay operates it substitutes resistance '|35 of equal Value for the winding of the other relay.

When a second in key is operated to the same position as the iirst "in key a second resistance, such as 529, is connected in parallel with the first, reducing the resistance value of the fourth arm almost by half. If the second in key is operated to the opposite position to that of the first in key, a secon-d resistance such as 529' in series with resistance |35 is connected in parallel with the first resistance and the relay 104 or '|05 so that the value of the fourth arm is halved. In either case the reduction in the value of resistance of this fourth arm results in a reversal of -current in polar relay 188. Relay "|88, upon operating, closes a cir-cuit from ground, armature and contact of relay 108, conductors 133 and 839 through buzzer 838 to grounded battery 831 and the buzzer operates to give an audible signal' that an error has been made in operating the switching keys. In a similar manner relay 6|2 uponY operating closes a circuit from ground, armature and contact of relay 6|2, conductor 839, through the winding of buzzer 838 to. grounded battery I831, the buzzer operatesto indicate that an error has been made in operating the switching keys..

A blown fuss applies grounded battery to the back bus-bar causing the fuse panel lamp to light and the fuse alarm plus relay 840 or the fuse alarm minus relay 84| to operate. The operation of either of these relays causes the alarm bell 83S. to operate until restored by the replacement or removal of the defective fuse or until shut off by the operation of key 842. Night alarm key M3l is-prcvided to cut the bell off the break circuit when an audible signal is not desired. The fuse alarm plus and fuse alarm minus relaysy 848 and 84| are protected by `fuses which also operate the alarm when the respective fuses are blown.

Testing A testing loop (not shown) is provided between the central oice and the switching panel equipment at the switching center. This test loop extends from the test board at the central ofce and terminates in two single line jacks connected. in series and mounted in the switching. panel. An idle pulsing relay such as relay 'H3 in group repeater GRA oran idle pulsing relay such as relay 688 in leg repeater LR9 or an idle` regenerative repeater element taken in conjunction with its associated pulsing relay such as relay I3 of group repeater GRA may be tested by Inaking suitable patch connections at the switching panel; At the switching panel are mounted for each group repeater a pair of test jacks. Test jacks TJA representing those assigned to group repeater GRA, test jack 'IJB represents those assigned to group repeater GRB, test jacks TJC represents those assigned to group repeater GRC, etc. Test jacks TJI, TJZ, TJ3 and 'I'JS represent those assigned to leg repeaters LRI, LRE,`

LR3 and LRI, respectively, for testing the pulsing relay in each repeater such as relay 588 assigned to legA repeater LRQ. When a patching cord is connected tol test pulsing relay 723, one end of the cord is inserted in jack A| of TJA and the other end of the cord is inserted in either of the two.- jacks terminating the test loop, the relays of group repeater GRA becoming operated as the result of' connected patching cords in a manner as hereinbefore described when an end key in was operated to the send, or left-hand, position. The polar testsignals of known bias sent from the central ofce over the ring of the test loop are repeated by relay 'H3 and sent back as open and close signals to the central oilice on the tip side off the test loop. In a similar manner, an idle regenerative repeater element and its associated receiving relay, such as relay 'H3 of group repea-ter GRA, may be tested except that one end of the-patching cord is connected to jack A2 of TJA and the. other end is connected to either of the test trunk loop jacks. The receiving relays of each of the leg repeaters may be tested, for eX- ample, relay 688 of leg repeater LRS by patching atest loop jack to jack TJ3. Or again, the overall transmission of theV combination of any one group repeater with any one leg repeater may be tested by operating the out key common to that combinationv and employingltwo patching cords, one of which is inserted at one end to Al, assuming that group repeater GRA is engaged in the test, and the other end of the patching cord is inserted in the rst of the two test loop jacks, and the other patching cord has one of its ends inserted in jack TJ 9 of the leg repeater LRS and the other end ofl the patching cord is connected to the second of the two jacks terminating the 'test loop. The particular send leg out key is operated, which associates leg repeater LRS with group repeater GRA. In this way the relays of a group repeater and a leg repeater are operated as in the manner hereinbefore described whenv an in key associated with one of the loops was'operated through its'receive, or righthand, positions and an out key associated with one of the other loops'was operated to its send, or left-hand, position. In this way routine' testing of the pulsing relays of any of the groups or leg repeaters may be made at the central cnice under the control of an attendant at'the switching center without interfering with traffic on the subscribers regular loops.

What is claimed is:

1. A signaling system comprising two or more transmission circuits each having two conductors, a plurality of switching means connected to each of said transmission circuits, each of said means having two operable elements, circuit means responsive to the operation, in either of two directions, of one of saidelements of one of said switching means and other circuit means responsive to the operation in one direction only of the otherY element of one or more of the other of said switching means for interconnecting for signaling purposes one conductor of one of said Y peating devices respectively connectable to each of said plurality of switching means, circuit means responsive to the operation in either of two directions, of one of said elements of one of` said switching means, and other circuit means responsive to the operation, in one direction only,

of the other element of one or more of the other of saidl switching means `for interconnecting, through the simple and the regenerative repeater of one of said devices and one or more of said other repeating devices, a conductor of the trans-` mission circuit connected to the switching means of which one of said elements is operated in said Y one direction and the other conductor of one or more of the other transmission circuits.

3. VA signaling system according to claim 2 wherein said circuit means comprise electromag` netic devices responsive when said one element is operated in either of two directions, other electromagneticY devices responsive when said other element is operated in one direction only and a circuit network arrangement provided for each of the first and the second-mentioned electromagnetic devices, said circuit network arrangements serving to cause the operation of an audible alarmy when anyconflicting operation of said switching means is made.

4. A telegraph system comprising two or more loop circuits each having two conductors, a plurality of switching means connected to each of said loop circuits, each of said switching means having Ytwo operable elements, -circuit meansresponsive to the operation, in either of two directions, of one of said elements of one of said switching means and responsive to the operation of the other element of any number of vthe'other of said switching means for interconnecting for transmission purposes one conductor of Vone of said loop circuits andthe other conductors of a corresponding number of the other of said loop circuits and' means connected to each of said one conductors of said other of said loop circuits for operating a distinctive visual and anv audible alarm when a break signal is received :from

. the distant end of any one of said loop circuits.

5.Y A telegraph system according to claim 4 wherein said means for operating the distinctive visual and the audible signal comprises an interrupter and timing circuit responsive to signals of a duration longer than the telegraph message signals. c

6. A telegraph signaling system comprising a plurality of at least three telegraph lines each having two conductors, the second of said conductors each having terminating repeating means, a plurality of combined simple and regenerative repeating means each common to said lines, and keyv operative means for selectively connecting one of said combined simple and regenerative repeating means operatively to one of a corresponding one or more of the remaining' lines.'

, 7. A Atelegraph signaling system according to claim 6 wherein the key operative means comprises a plurality of parts, one part having cir.y cuit closing instruments arranged, rst, when said part is operated in one direction to connect the simple repeating means of said combined repeating means to one of the conductors of a call- Y ing one of said lines, and secondly, when said part is operated in the other direction to connect said combined repeating means to the other of said conductors of the calling one of said lines, and another part having other circuit closing instruments arranged when said other part is operated to operatively connect one of said terminating repeating means to Vsaid second one of the'conductors of one of the remaining lines and to said simple repeating means or to said combined repeating means as determined by the direction of operation of the first-mentioned part of said key operative means.

8. A telegraph signalingrsystem comprising a telegraph line having one Way terminating repeating` means, a plurality ofy other lines each having one way terminating repeating means, a plurality of one-way regenerative repeating means each common to said lines, keyV operative means for selectively connecting said telegraph line through anyone of said regenerative repeating means to the terminating repeating means of one or more of said plurality of lines for oneway transmission.

9. A telegraph switching system adapted for broadcast purposes, comprising a central oiiice, a switching center, a plurality of line circuits interconnecting said central office and said switch-` ing. center, each of said line circuits having a send conductor arranged for transmission in one direction and a receive conductor arranged for transmission in the other direction, a plurality of key-controlled circuits normally connected in series to each of said line circuits at said switchingA center, a line circuit repeater connected to the last one of one of said key-controlled circuits and aplurality of group repeater circuits each connected tothcse of said key-controlled circuits that 'are connected to different line circuits. I V,10. A telegraph switching system adapted for broadcast purposes and comprising a central oiice, a switching center, a plurality of line circuits interconnecting said central oflice and said switching center and each of said line circuits comprising a send conductor arranged for transmission in one direction and a receive conductor arranged for transmission in the other-A direction', a plurality of key-controlled connections normally connected in series to each of said lineY nections to transmit to one or more send conductors of the remaining line circuits, a line circuit repeater for each of said line circuits and connectable through two or more of said keycontrolled connections While repeating signals from one of said transmitting and receiving means to one or more send conductors of the remaining line circuits, a plurality of group regenerative repeaters common to said line circuits, each of said group repeaters being connectable through two or more key-controlled connections for regenerating signals incoming over said received conductor and for transmitting said regenerated signals over one or more send conductors of the remaining line circuits.

l1. A telegraph system adapted for broadcast purposes and comprising a central oflice, a switching center, a plurality of line circuits interconnecting said central ofce and said switching center, each of said line circuits including a send conductor arranged for transmission in one direction and a receive conductor arranged for transmission in the other direction, a plurality of key-controlled circuits normally connected, in series, to each of said line circuits at said switching center, a line repeater connected to the last one of said key-controlled circuits connected in series, a plurality of group regenerative repeaters, circuits of each of said pluralities, means included in each of said key-controlled circuits of each of said pluralities for connecting a different one of said group repeaters to one of said line circuits and other means included in each of said key-controlled circuits for connecting any one of said group repeaters to one or more of said line repeaters for transmission over one or more of the remaining line circuits.

ALLEN R. BONORDEN.